Transmission control circuits



Jan. 19, 1932. H. w. DUDLEY 1,841,405

TRANSMISSION CONTROL CIRCUITS Filed Dec. 4, 1930 SUBMA R/NE CABLE INVENTOR By H. M. DUDLEY A TTORNEY Patented Jan. "19, I, r

HOMER w. DUDLEY, F meson-meme ,Jmsm s'siemg o ii Ln L i=3bN "1., A c0 l oRAT'lOrr cjn LABORATORIES, meonronernn, 0F YORK,

Your:

Application filed DceemberA, 'iee'o trolling transmission-' in signaling systemsand particularly to circuits for reducingthe effects of; interfering waveson the {operationtheg-'coinbined waves a difierent-frequency iii'of such transmission "c0ntro1 circuits An object of the invention is to "discrim-c inate between electrical'wavesoi: diflerent characteristics, for example, between useful signals and interferingnolse waves.

10 Another object is to improve the operation;

of Signal-controlled devices for suppressing echoes and preventing singing in two way signaling systems subject to interfering; waves, for example, resistance noise waves The invention inabroad aspect isasystein; for discriminating between waves on the basis of difi'eren ces intheirenergy character:

istics. More specifically stated it is a system for discriminating bet-Ween wave'shavingan energy spectrum'whichinay be considered as discrete, for example, speechl wavesj and: waves having a substantially c0ntinuousen-- er s 'ectruni over adefinite-"ire uenc sistance noise waves.=

Resistance noise has an infinitesimal amount of power at any frequency so thatifg r the frequency bandof the waves' transinittedi over a signaling line issubdivided, intoa number of sufficiently narrow sub-bands, the amount of power due to resistance noise; in each sub-band maybe reduced to a desired small value. On the other hand i'n the case of a vowel in speech: (and'in a lesser degree} in the case of speech in general) a frequency; 1

range however small will contain finite power provided that one of the discrete frequenc es 40 of the vowel (or speech) is presenttherein.

-The circuit of the-invention based on thef above mentioned characteristics, comprises" e ement ome wem range, for example, waves 7 due to thermal agitation in electric conductors,so-calle'd re .tein, employing transni Therefore, by selecting from the combined speech and noise wai'es transmitted over a:

speech, in an ideal case any desired amount power may be "objri K654993361 V7 p wave controlled apparatusfconnected across the i-transnnssion' path carrying: the signals and the interfering noisewave s, through one: I a

or more'selectiv'e circuits eachselectingfrom hand ofsuch smallfwidth thatthemagnitude of: the; energy therein dueto noisefwaves is too'sinall to operate the associated. device,"i

which, lioweve'r,-'wil1 be, operated by! the en ergy of the gsignall'waves'in theiband a; discrete frequency is present therein. Asufilcient" number ot-these circuits inay' be pro crate th'e wave c'ontrolled device.

vided so' that when: the transmission .path is transmitting the" signalsat least a one of the selected bands will contain a discrete 3 signal frequency which "has s'nfiicient power to lop Y The circuit o'fthe" inventionfniay be 'apif plied-to advantage in: alongtwo-way signal-w ing system, such s atwo waygtelephone or submarine telephone: cable-system; fmpljoy-* 7 ing signaleontrolled devices for determining the 'di'rection ottransmission, to preventfalse operation of such devices? byv the noise waves wl'i ile' maintaining them at maximum sensi-l' Y objects and; advantages of the inven-q lie-better underst'codxfrom the for lewing detailed description? thereof when; e0; drawing} the single: figure of which shows read: ceiinectien; with the accompanying:

oneterniinalof a' long two-way signaling sy'stem, such asasiib narineftelephone cable syss J j The terminal circuits shown n the draw- I ing coinprisei a transmitting circuit TC in Waves received-over the land line LL intofthe' vices l Bland 4 for transmitting in i'aniplified form signal waves received {over thesuhrf marine cable circuithiSG" intothe landteleiphone line LL. Thejinputgof the transmitting circuit and the output-10f thei'ree.

gaterelation witheach' othefand in energy, transmitting relation with thelandtelephone ssion control circuits iembodying:the 1nvent on f ceiving' circuit RC La-re 'asseciated in conj 11 I 751 i 1 tivity'as regardsoperation by useful signals; 5

line LL byim'eans of the hybrid coil H and associated-balancing network N in the man-' ner wellknown in the art.- The output of the transmitting circuit TC and'the input of the receivingcircuit' RC7 are directly connected to the west cndof the submarine cable '7 Ivice 2 therein is the input of a control'cir-' cuit 5 comprising the wave-controlled, re-l lay-controlling device 6, and the windings Connected across the transmitting circuit Y TO'between the outputof the amplifying device'l and the input of the amplifying deof the mechanical relays 7 and8 connected in parallel'to the Output of the device 6."

In the transmitting circuit TC between the output of the amplifying device 2'ther'ein and the submarine cable circuit SC are r the normally open-contacts of a switch 9' ar ranged tofbeclosed by operation of the relay 7 .3 In thereceiving circuit RA between the submarine cable circuit SGand the input of I the amplifying device 3 are the normally closedcontacts 10 of a switch arranged to be opened by operation of the relay 8.. I

- r Connected-across the rece ving circuit RC betweenthe output of the amplifying device 3 andtheinput ofithe amplifyingdevice 4 therein is a control circuit '11 comprising the one-Way amplifying device 12 and a plurality of auxiliary circnits S S2 and S connected in' parallel across the output of theidevice 12. .Theamplifier dev'ice12 is not necessary if the wavesdiverted into control circuitrar'e. sufficiently amplified by the amplifier 3 in the circuit RC. If the device 12 is not used the-selective circuitsS S and S; are connected inparallel directly across the receiving circuit RC. The auxiliary circuit s comprise's the selective circuit' 13 connected. to the. output of the connected to the output'of the device 14..

amplifying device 12, the wave controlled,

relay-controlling device, 14 connected to the output of theselective circuit 13,-and the windings of. a 'mecha'nical relay 15 The auxiliary circuit 8 comprises the selective circuit 16 connected to the output of the amplifying" device ,12, the wave-com,

trolled, relay-controlling device 17 connected to the outputof the, selective circuit 16, and the windings'of a mechanical relay 18 con nected tothe output of the device 17. Simil arly, the auxiliary, circuit S comprises the selective circuit 19 connected'to theoutput of the amplifying device '12,.the wave-controlled,relay controlling device 20 connected to the output of the selective circuit 19, and

the windings of a relay 21 connected to the output of the device'20, c

7 Relay 15 is adapted cooperate in response to'the energization of" its windings by operation ofthe device 14: to close its contacts 22 so as to short-'icircuit'the control circuit 5 at a point therein between the device 6 and the 1 41 405 i v I V windings of relays 7 and 8 Relay18 is adapted to operate in response to the energization of its windings by operation of the device 17 to close its contacts 23 so as to independently short-circuit the control circuit 5 at'a point therein between the output of the device 6 and the'windings of relays 7 and 8. Similarly, relay 21 is adapted to operate in response to the energizationof its windings by operationlof the device 20 so as to independently short-circuit the control circuit-,5 atapoint therein between theoutput of the'devicef6and the windings of relays7and8.

It is apparent that the terminal circuit which has just been described is of the type knowninthe art'as semi-biased, that is, thecircuitis normally operative to transmit in one direction (in this. case from the submarine cable SC into the land line LL over thereceivingfcircuit RC) and transmission in the, opposite direction (in this case from the-landline LLinto the submarine cable SC over the transmitting circuit TC) is dependent upon a switching operation,

'The, wave-controlled, relay-controlling devices 6,14, 17 and 20 maybe vacuum tube,

amplifier rectifier devices of the type well known in the art or any other devices which will respond to alternating current impressed upon their inputs. to -contro'l the. operation of mechanicalrelays connected to their outputs; h I 1 I r The selective circuits 13, 16'and 19 may bereso'nant'circuits of the type well known in the art,feach tuned tofa: selected different frequency withinthefrequency range of the waves impressed upon their input from the output of the'amplifying device 12, so as to transmit to the windings of'relays 15, 18

and 21 respectively with little attenuation the resonant and neighboring frequencies in the'impressed; waves, while producing, appreciable attenuation in other frequencies of the impressed waves. Alternatively, the selectivelcircuits 13, 16 and 19 may be band-- pass-filters of wellknown type, for example, such as disclosed inU. S. patents to Camp-c .bell 1,227,113and1,227,114, issued May 22,

1917, in which case the filters are designed to transmitrespectively to the windings of relays 15, 18*and- 21, with little attenuation a different sub-band of frequencies within the frequency range of the waves impressed upa quencies from the vwaves impressed on the ceiving' circuit RG extending 'ironi quency ofsay l209-cyclesito a frequencyfof trol circuit 5. p

however, which will get through to; [the 111+- lLOOcycIeS per second; Won-Idiot course qc'on tain several discrete speech frequencies; If; therefore, the selective circuits 133 16 and 19 vare utilized to respective-1y iselect a different frequency sub-bend -within'-t1f1is frequency range, zit-least one of the sei'eCte'dS 'bandsJ would co'ntaln discrete speech frequency which would contain appreciable power; The

sub-bends, however, fare; of such nurroW W dth that-the power due to IESlSiEELIlCH'IlOlSef v waves contained in' any one ot-Q; them would; not be appreciable. Iftheein Iifierrectifier devices 14, 17" and 20. therefore? are normally adjusted so as. to be normally; inoperative by. I the amount of'powerdueto: resistance noise, p p p p Tc wlli fbfi emphfiedz bythat 'a nplifiercandyz transmittedidirectly into the submarine contained in anyone of the sele'ctedfs'ub};

bands, but to be operated [by the amount, 0:61 power contained in "a discrete s eech; fre quency, it is apparent'fthati et .1eas t -one oi? the relays'15, 18 and 21;,ccnne'ctedintheoutr. put of the devices 14,17: and 2.0 respectively will operate in response to the speech. waves from the output of-the amplifier 12. to1c1ose its contacts and thus ShOIt-CllClllfi thQ'COIl-g The. resistance noise iWttVGS,

puts of the relays .15, 18- end 21'willn0thave sufiicient power to operate any oneofithesez relays. The control circuit 11 eonnecteddtof the receiving circuit RC, therefore,efl'eetivey i 1 t ereet:

edeyice BJ rthe eLay-S'Tand 8'con'nected1 t the-routputthereof should be designed-so T 1y discriminates between the speech aves' impressed u-ponxlts input end-interfer ng ncise Waves, so thetfalse operation ,of-vthe receiving switchingcircuits'bynoise; iSfQf" v Y w en fectivelyprevented. 1 e 1 It is of course evident that ife g reaternum ber of. select ve c rcuits are used; thejchance of a. frequency sub-band?selecte'd by jone of;

j the selective circuits containing atleast onei V of the amplifier A will be idivided' between.

discrete speech frequency ofsuificient pow veri cooperate the associated short-clrcint ng} lay is greatly 1ncreesed,'jand, tcourse f;

the selected bendin. the output of the 21111 plifier 12is subdivided into; a greater number 7.

of small sub-bands, theeinount of poiver in any one band due to the res stance no se: 111 be greatly decreased amount of protection-"against: noise 'nialyi obtained- ,by suitable [choice of; the 'piujiiaer,

number of the selective-circuits end asso' eted apparatusi:

.; y 7 Theopera-tionof at Whole will nowlbe described. Speechwayesr together withtheaccompanyingnoise vev it a receivedjover the land line LL will pressed by the hybrid icoilf l l uponthe. mitting circuit TCendemplified bythe an plifying device/l therein. Theeniplifiied' speech Waves and noisejveves in. th'eloutput the inputof the amplifier. 21in the" t'ransm' p ngv et fhefc ntrel ir uit tra n 1 7 Thus any desired (Eu-i655 'The; portion divertedintothe con tr circuit' fi willfoperete the we've-controlled,-

controlling device 6 therein causing. the

circuit thereafter inoperittive to transmit rei celved waves from the. submarine cablecir- 1 cuit' tp ithez'land line-4H3. Relay Twill immediately thereafter operate to close the inormaillyopen switch. 'c ntactsQ in theout put of tliejtransn itting circuit TC; thereby making a that; circuits Loperetive tofitra'n'smit' speechi xvavesi-f om theaoutput of the .ampli c Her 2 into thesubmarine cable SC. put ofl aamplifier' 2- 5in the transmitting circuit the witch contacts; 9. being inow: closed, will The portion of the, speech Waves, inthe in" I i s cable :circuit SG and" transmitted lthereover; to y j the? receiving station at 1 the other end there'- off; it is ofjcourse-necessary that the contacts 9Q TC'be-fclosedbefore thespee'ch Waves arrive Shin-the output-0f the transmitting circuit zit/that point in thegcircuit, i ltiniay be-desir-' able. therefore toihsefrt' 2 delay. circuit: of any of ;,tlie: fwel'l ki iown t ypes in the "transmit-ting z i cui t TQbetLWeenthe-point ofconnectionof t 1.

theycontroljcircui'tfi' tiieretoand the switch 9 V condition when I the speech} wa ves have; a given amount of p, hangover in "der to; insure that '1 the (contacts '9 are in, 1

in-order that, eifter the transmission H oi:": spee,ch a-ves from-the pathqTO into the control circuit ceases, a the transmitting czr it 1 0, iwil uremeiu un te id-t ceivlngtclrc-uit Bc noperetlve for a sutficient d l l n l ale re hw ime -t P v t aves 1 received over the submarine cable SC ip ni i elet he te min 'e r i t w b t te d iansmittlngcircuit TC being '11 b e divided between the.

ricuit 1 11. "The main lpo-r 4 in;thetreceivingcircuit RC and transmitted plifiedbyf'the'einplifyingi de v 'm ufiedwa'ves in the output 3 r f 111g de'vice and the in disgi '11 olutput byvthe open switch contacts Th Wax resin thereceiyingcircuit'- r Of ne s hiw l l lei l l he tp f amplifier 3'wi1lbean1p'1ifiedby the amplifier: thereover.to;th hybridl'coiLH and impressed 1 thereby on "lundlline i LL (over which "it ,Will i 'b isnlijtted "to; the: listening,- sub:

will select a different frequency sub-band ofthe impressed waves, "withina given fre-i quency range, for example,"within thejfrequency range'sextending from 1200 .to 1400; cycles-per second. 'As the selected'bands,

the amplifier?) including the speech waves and the interferingjnoise waves diverted into thecontrol circuit 11.will be amplified by the amplifying device-12 therein, and the amplifiedzwaves will be divided between the paral-' lelauxiliary circuits S S and S 7 Eachv of the selective circuits 13, 16 and 19 1 have such small width, the energy due to recient to operate thecontroldevices 14,17 or sistance'n'oiseinlany one of them is not sulficonnected tothe output .of the selective circuits";

Because of the small width of the selected sub-bands,-the energy duet'o the speech Waves i 'ltherein will also be of insuflicient magnitude to'operateany of the; devices 14,17 and '20 unless there should happen to be one or more discrete speech frequencies of appreciable energy content in one or more of the selected bands.

7 discrete frequency in the band selected by windings of relays 7 and'8. Only oneshort the selective device 13. The control device 14' will be operated bythis discrete frequency and the windings ofrelay 15 in its output en- Y Z ergized so as to close the contacts 22 to shortcircuit the control circuit '5 between the output of the 'device'6 and the input of the relays T-and 8. If there should be additional'dis- V crete speech frequencies in the bands selected by 'selective circuits 16 or 19, the corresponding relays 18 or 21 will operate in'consequence of the operation of control devices 17 or 20jby the additional discrete frequencies to close their contacts 23 and 24, and thus to close additional short-circuits across the control cir-" cuit 5 between the output of device 6 and'the circuit across path 5, of course, is necessary to prevent operation of the device 6 therein by waves or noise energy from the transmitting circuit TO from causing false 'oper'ationof relays 7 and 8 to respectively close the trans mitting circuit TC and open the receiving circuit BC by closing the contacts 9 and open- I ing the contacts 10 in the respective circuits.

The control devices 14, 17c and 20 or" the relays 15, 18 and 21 should be designedito" v have sufficient hang-over in their action so as i tomaintainthe 'short-circuiting contacts 22,

23 and 124 closed for theproper interval of time after the input of the speech waves to theamplifier '12 in control circuit'll ceases, so

as toprevent false operation ofthe relays 7and8. V

isto be understood that the invention not limited to the particular circuit or the' details of the terminal station illustrated and described since numerous modifications may 7 be made therein by persons skilled in the art without departing from the spirit and-scope Let it be assumed that there is such a ofithe invention-.{ -;Although the terminal circuit illustrated and described comprises a normally operative receiving circuit, a normally disabled transmitting circuit and switching means responsive to' energy to be I transmitted over the cable to make operative the transmitting circuit and toidisable the receiving circuit' and switching means r'e sponsive to energy received over the cable SC for disabling the first" mentioned normally operative switching; circuit,"the invention is not limited to these; details. For example, the invention is applicable as well to such cir-' cuits modified so as to'comprise a normallyv disabled receiving circuit, a normally operative transmitting. circuit, switching means respons'ive to energy. received over the cable for disablingsthe transmitting circuit and rendering-operatiVeEthe receiving circuit, and

switching means responsive to energy to be transmitted out overthe cable for disabling the first. mentioned -normally operative;

switching means. v

1 In the particular embodiment of the invention illustrated and 7 described, current-controlled mechanical relays are employed for producing an open circuit in,-or a short-circuit across a transmission path to disable it or closing an open circuit or'openinga shortcircuit to make it operative, it is to be understood that the invention is not limited to conditioning means of this type. For example,

Within-the scope of the invention the transmission pathrnay be conditioned by utilizing current-controlled relays to disable the transmission paths by inserting losses in these don) 'vol 20, pages'65 to 72' inclusive, publlO lished in April, 1927, or in the s. patent to r Crisson 1,647,212, issued November 1, 1927 A signal receiver subject to combined alternating current waves including'useful signal waves having a" discrete frequency spectrum and interfering waves which over a definite frequency range have a substan tially-"continuous energy spectrum, comprismg SBlBCtlVQ means for select-mg from the frequency bandofsaid combined waves one or more .narrow sub-bands within said de finite frequency range, one or ,more wave rectifying devices, means for impressing eacli of'the selected sub-bands on a different one ofsaidrectifying device's, eachof said devices beingadjusted to inoperative for in]; v pressed energy of anamount corresponding t'o'that due to said interfering waves contained in the selected sub-band impressed,

thereon but to operate in responseftothe greater amount of energy which wofuld be contained in a discrete signal frequency of I the selected signal waves, and signal receiving means responsive'tothe rectified energy produced by operation of' any oneof' said rectifying devices. j V 2. A signal receiver according to'claim l and in which said selective means comprises one or more electrical wave band-pass filters. 3. A terminal for a two-waytelephofie transmission line comprising transmitting and receiving circuits connected to said line, means responsive to telephonic waves to be transmitted over said line for varying: the transmission efficiency of at least one of said unresponsive wan amountof impressed war'fe energy corresponding to that due to the interferingwaves inthe frequency sub-band impressed thereon-but tocoper'ate in response to a greater amount of energy which would be contained a' discrete frequencyof speech if present inthe impressed sub-band.

In witness whereof, I hereunto' subsc'ribe" Qnd'day of December, 1930.

my name this 7 v a DUDLEY;

circuits, aplurality of wave-controlled 'dea vices responsive to received Wave energy of a given amount to independently controlsaid f transmission efiiciency varying means, means for selecting and supplying to each of said wave-controlled devices, adiiferent band of frequencies of the combined telephonic; and speech waves receivedcover said 'line, each band having insuflicientenergy due to said noise waves to operate the associated wave-h controlled device, but at leastone of said bands having one or more discrete'speech fre-- quencies of the received telephonic waves containing sufficient energy tooperatefthe associated wave-controlled device. 4. The terminaliof claim 3 and in which the transmittingcircuit is normally disabled and the receiving circuit'normally operative,

said transmission efficiency-varying means comprises means for effectively disabling said receiving circuit, and for rendering 's aild transmitting circuit operative, and sald wave,-

control devices are responsive to received waveenergy of said given amount to effectivelydisable said transmission efficiency: 7

varying means. i

5. A terminal for a two-way telephone]; transmission cable subject to interfering noise 9 waves which over a definite frequency range,

have a substantially continuous energy spectrum, comprising transmittingand recelving circuits connected to said line, means responsive to telephonic waves to be transmitted over said cable for varying the transmission efficiency of one of said circuits, aplurality of i transmission devices responsive to, rectified wave energy impressed thereonto independf ently control said transmission-efiiciency varying means, a plurality of selective means,

connected in parallel to thereceiving circuit and'each adapted to select a diiferentnarrow' frequency sub-band of the alternating current waves received over said cable, a plurality of wave rectifying devices each controlling one of said transmission devices, and means for impressing one of the selected sub} bands on one of said rectifying devices, each rectifying device being adjusted so as to be j 

